Damper assemblies are a common part of Heating, Ventilation, and Air Conditioning (HVAC) units. A damper assembly may have two parts: an outdoor air section which opens to receive outdoor air from outside the building, and a return air section which opens to receive return air from inside the building. Opening one section of the damper assembly may close the other section and vice versa.
A HVAC unit controller adjusts a damper assembly to optimize energy use. For example, suppose a HVAC unit is cooling a building, and the outdoor air is cooler than the air inside the building. It is more efficient for the HVAC unit to condition the outdoor air than to condition the return air. Thus, the outdoor air section should be open at least partially. An opportunity to save energy would be wasted if the outdoor air were kept out of the HVAC unit. Using outside air to cool the building in this manner is known as “free cooling.”
Similarly, when cooling during hot outdoor weather or heating during cold outdoor weather, it is more efficient for the HVAC unit to condition the return air. The outdoor air section should be closed and the return air section should be opened. Otherwise, the HVAC unit would waste energy cooling or heating the outdoor air instead of the more suitable return air.
A damper drive train opens and closes the sections of the damper assembly. A damper motor moves the damper drive train. The HVAC unit controller sends command signals to the damper motor to control the movement of the damper motor.
It is possible for the damper motor to become mechanically disconnected from the damper assembly and damper drive train. When the damper motor is disconnected, the HVAC unit controller command signals cannot open or close the sections of the damper assembly.
Energy savings can be missed if the outdoor air section is left closed due to the disconnection. The HVAC unit may be missing the opportunity to utilize outdoor air which is more suitable for cooling than return air. Likewise, energy can be wasted if the outdoor air section is left open due to the disconnection, because the HVAC unit may unnecessarily heat or cool the less suitable outdoor air instead of the return air.
Conventionally, a disconnected damper motor is discovered, if ever, by an onsite technician visually inspecting the operation of the damper assembly. The HVAC unit may operate for a significant amount of time before a technician discovers the disconnection. It would be desirable if a HVAC unit could detect a disconnected damper motor automatically. The disconnected damper motor could be repaired more quickly, allowing the HVAC unit to resume moving the damper assembly.